GImpact collision algorithm is not dispatched in contactPairTest

[i-to]

Reproduction sequence:

1. Setup btCollisionWorld.
2. Register GImpact algorithm via btGImpactCollisionAlgorithm::registerAlgorithm.
3. Create two collision objects containing btGImpactMeshShape shapes, add them to world.
4. Invoke btCollisionWorld::contactPairTest for two objects.

Result: btEmptyAlgorithm stub is dispatched for testing and actual collisions are never reported.
This behavior appeared in commit 9ee1c4e. In earlier versions, GImpact algorithm would be used.

Would it make sense to rename btCollisionWorld::contactPairTest to closestPointPairTest
and then use BT_CONTACT_POINT_ALGORITHMS in contactPairTest for algorithm lookup?

[jrz371]

As a workaround you can update your collision objects, call performDiscreteCollisionDetection on the collision world, then iterate over the manifolds in the dispatcher. This should at least give you the collisions.